The present specification generally relates to inactivity timers triggering the shift of network elements from a kind of an active state (e.g. connected state) to a kind of an inactive state (e.g. idle state).
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) and its successor LTE Advanced (LTE-A), all provided services are of packet switched (PS) type and thus are finished. In case there is no non-GBR E-RAB (GBR: guaranteed bit rate, E-RAB: evolved radio access bearer) any longer established for a terminal like a user equipment (UE), the UE moves to ECM—Idle state (ECM: EPS connection management, EPS: evolved packet system), and RRC—Idle state (RRC: radio resource control) is triggered by inactivity timer expiry at evolved NodeB (eNodeB, eNB) side (unless before the release was already initiated for any cause either by eNB or evolved packet core (EPC) which may include “user inactivity” cause and may also be different from “user inactivity” cause).
The services can be divided into two groups considering the time between a newly successful RRC connection setup and the last (preceding) RRC connection release. The first group is constituted by services in relation to which this considered time (between a newly successful RRC connection setup and the last (preceding) RRC connection release) is quite long (e.g. tens of minutes or hours). The second group is constituted by services in relation to which this considered time (between a newly successful RRC connection setup and the last (preceding) RRC connection release) is e.g. tens of seconds.
A typical example of the service from the first group (first type of service) can be a voice over LTE (VoLTE) call with a common characteristic that                data transmission is accumulated into the time period the call is active without any long interruptions (pauses), and        there is a sufficiently long period between two consecutive calls from/for the same UE.        
On the other hand, a typical example of the service from the second group (second type of service) can be web browsing with a common characteristic that                data transmission is accumulated into smaller time periods in which the service is active i.e. with long interruptions/pauses between data transmissions.        
In the past, operators had only option to set the inactivity timer commonly for all kind of services.
This may lead to the situation that for the services from the first group, the UE had to spend ineffectively longer time in RRC Connected state which had negative impact on UE's battery live. On the other hand, for the services from the second group, the inactivity timer setting can be insufficient which then may lead to significant increase (in the number) of the UE movements/shifts from RRC Idle state to RRC Connected state.
Presently, two types of inactivity timers are configured for the services from the first and second group, respectively, to overcome the above outlined issue, namely short and long inactivity timers.
Additionally, it is possible to provide more than two groups with services grouped according to QCI characteristics (QCI: QoS class identifier, QoS: quality of service).
It is known that inactivity timers may have influence on several network related quantities which may affect the traffic management effort, the available payload bandwidth, as well as the energy consumption of mobile devices, for example time in RRC connected state after completion of data transmission, number of movements of mobile device to RRC idle state, number of RRC connection setups for the mobile device, etc.
Hence, the problem arises that a flexible configuration of inactivity timers is necessary in order to achieve optimized effects on the mentioned and other network related quantities.
Hence, there is a need to provide for inactivity timer evaluation.